Brake means for rotary variable resistor



29, 1966 R. 1.. JONES ETAL BRAKE MEANS FOR ROTARY VARIABLE RESISTOR Filed March 4, 1964 FIG. 5 0,

INVENTORS Roe/52 L. Jo/vss, HAROLD L. KHz/s5 United States Patent 3,289,137 BRAKE MEANS FGR ROTARY VARIABLE REISTOR Robert L. Jones and Harold L. Krnse, Riverside, Calif, assignors to Bourns, Inc, a corporation Filed Mar. 4, 1264, Ser. No. 349,296 '2 Claims. (Cl. 338162) The invention hereafter described and explained pertains to potentiometers, and more particularly to potentiometeis having a rotatable member that is rotated to effect variation in the resistance between, or the potential difference exhibited between, terminals of the variable resistor.

A variable resistor of the type mentioned comprises a resistance element of helical form having an exposed helical contact surface or zone that is brushed by a wiper contact incident to relative rotation between the element and wiper contact. The rotatable one of the just mentioned active electrical components of the variable resistor is rotated by a knob-like structure or device that is exposed for manual operation. Typical of the helical element and wiper constructions noted are those illustrated in Patents Nos. 1,621,466; 2,813,956; 2,815,422; 2,871,326; 2,863,- 501; 2,839,643; and 2,853,586.

In many instances variable resistors or potentiometers of the class noted are used in fixed stationary apparatus not subject to vibration or other disturbances that may undesirably change the setting or adjustment of the instrument. However, in some applications, the potentiometer or potentiometers may be subjected to very severe vibration, and as an incident thereof the setting or adjustment easily could and generally would be changed by vibrationinduced relative movement of parts or components.

The present invention provides simple inexpensive readily operated means that permit locking and releasing of the rotatable device of the resistor, irrespective of the position or extent of adjustment of the rotatable device. As herein illustrated in exemplary form the noted means are applied to a known potentiometer in which the active electrical elements including the helical resistance element are enclosed within a knob-like rotatable shell that is manually rotated to effect adjustment of the resistance or potential exhibited between terminals of the instrument. The latter particular exemplary potentiometer structure is fully depicted and described in US. Patent No. Re. 25,674, the disclosure of which patent is herein incorporated by reference and to which reference may be made in respect of details of the potentiometer structure per se that are not herein specifically shown and described. Essentially the invention provides a stationary member having an externally-threaded cylindrical portion integral with a plurality of resilient tapered grips, and an internallythreaded ring member the threads of which are complementary to those of the stationary member and engaged therewith, and the ring member having a circular cam surface adapted to engage the tapered grips and move the latter into locking engagement with the rotatable adjusting member of the variable resistor as the ring is rotated in a first direction, whereby to lock the latter against unintended rotation. Rotation of the ring in the opposite or second direction is effective to unlock or release the adjusting member. Both of the components of the locking structure, that is, the stationary member and the ring member, may be very inexpensively formed of easilymolded material such as diallyl phthalate, nylon, Nylatron, or Zytel. The parts may be added to existing known potentiometers of the type depicted in the aforementioned Patent No. Re. 25,674 and other devices having similar rotatable adjusting members, either at the time of assembly of such potentiometers, or afterward. Preferably the stationary member is so formed as to be held in place by Patented Nov. 29, 1966 the structure that secures the potentiometer or variable resistor in place.

The preceding brief general description of the invention makes it evident that a principal object of the invention is to provide improvements in variable resistors of the type using a knob-like device for manual adjustment.

Another object of the invention is to provide simple inexpensive means for maintaining the setting of the rotary adjusting member of a potentiometer.

An additional object of the invention is to provide means for preventing undesired rotation of a rotary potentiometer, which means are held in place by the potentiometer whereby the means cannot become detached and lost.

Another object of the invention is to provide an improved potentiometer of the type having a multi-turn helical resistance element contained in a knob-like shell that is manually rotated to adjust the potentiometer.

Other objects and advantages of the invention will be hereinafter made evident or set out in the appended claims and explained in connection with a detailed disclosure of a preferred exemplary physical embodiment of the invention as it is illustrated in the accompanying drawings, in which drawings:

FIGURE 1 is a pictorial representation depicting the preferred exemplary physical embodiment of the invention mounted on a fragment of a panel;

FIGURE 2 is a side view of the structures depicted in FIGURE 1;

FIGURE 3 is a face view of the structures depicted in FIGURE 1;

FIGURE 4 is a face view of the stationary member of the means for preventing undesired change of adjustment of a potentiometer contemplated by the invention, as illustrated in FIGURE 1 but to a different scale;

FIGURE 5 is a partial-sectional side view of the member illustrated in FIGURE 4, the section being as indicated by the line and arrows 55 in FIGURE 4',

FIGURE 6 is a face view of the rotatable ring-like member that is manually operable to first and second positions to prevent rotation, and to release, respectively, the adjusting device of the potentiometer depicted in FY- URES 1, 2 and 3;

FIGURE 7 is a partial-sectional side view of the member depicted in FIGURE 6, the section being taken as indicated by broken line 7-7 in FIGURE 6; and

FIGURE 8 is a fragmentary sectional view illustrating one means for preventing rotation of a stationary member comprised in the exemplary structure.

In FIGURES 1, 2 and 3 a potentiometer of structural characteristics like or similar to that disclosed in the aforementioned Patent No. Re. 25,674 is shown with additional structures or members according to the present invention, the potentiometer being mounted on a panel P such as may form the face of a console or the like. The potentiometer, which is shown to an arbitrary and unimportant dimensional scale, comprises a rotatable part in the form of a generally cylindrical shell 14 closed at the front by a transparent crystal 32 and rotatable upon stationary supporting structure that includes a stud 10 (FIGURE 2) that extends through an aperture in panel P and is part of means by which the potentiometer proper is secured or mounted on the panel at a particular location on stud 10, all as more fully explained in the noted patent to which reference can be made for details of the shell, mounting means, and other known structures including a stationary helical electrical resistance element 16 and a rotatable wiper contact device 26 connected with and operable by rotation of shell 14 and having therein a rotatable electrical contact element.

Held in place between the front face of the panel P and the shell 14 is an annular cup-like stationary member 60 (FIGURES 4 and 5) that comprises a fiat annular portion 6tI-r that is integral around its outer periphery with a forwardly-extending somewhat cylindrical fiange portion 600. The flange portion 60c bears an external screw thread 601, which as shown is a left-hand thread; and forwardly of the threaded section the flange portion is tapered as indicated and longitudinally and radially slotted at a plurality of circumferentially spaced places as at tis to provide an annular series or set of resilient grips such as 60g having respective inclined cam surfaces 60m. The fiat rearward disc-like portion 6dr of the stationary member 60 is provided with an aperture 60a so dimensioned and situated that it snugly receives an annular flange portion 10s that is provided on or around stud 10, whereby the member 60 is supported on the supporting stud or bushing of the potentiometer with flange portion 600 disposed in coaxial relationship therewith and concentric with the rotary adjusting member (shell 14) of the potentiometer. Portion 60r of the stationary member 60 preferably is also provided with a small aperture 60b dimensioned and disposed to receive an antirotation pin or the like that is received in a complementary hole in the panel P and which anti-rotation device acts in well known manner to prevent undesired rotation of the stationary parts of the potentiometer. The inside diameter of the cylindrical flange-like portion of stationary member 60 is such as to be just slightly larger than the outside diameter of the rearmost part of the potentiometer adjusting member (sleeve 14), as indicated in FIGURE 2. Thus when the grips 60g are forced radially inwardly by means presently to be described, they individually frictionally engage the outer surface of the adjusting member.

Mounted for rotation on the threaded rear cylindrical section of member 60 is an annular ring-like rotatable member 70 (FIGURES 6 and 7), that hereinafter may be termed a ring in the interest of brevity of expression. Member 70 has an internally threaded rearward section 7tit whose screw thread is complementary to the external screw thread Gilt of member 60, whereby member 76 may be rotated, and thereby forced to axially translate, upon member 69. As an aid to manual rotation of member 70, the exterior surface is preferably milled or provided with ribbing 7 m or the like. The member 79 has a threadiess relatively smooth plain cylindrical forward portion 70d that provides a circular cam 700 or portion that is adapted to move onto the inclined outer cam surfaces 60111 of grips 69g and force the outer ends of the grips inwardly to produce the previously mentioned frictional engagement between the grips and the potentiometer adjusting member or part, 14. Since member 60 is held against rotation by means such as the noted anti-rotation pin, grips 60g, when tightly gripping part 14 lock the latter member against rotation. The thin rearward portions 6011 (FIGURE of the grips 60g are resilient, and yield as springs when the grips are forced radially inward into firm frictional engagement with member 14 as the circular cam 79c moves forwardly incident to rotation of ring 70 in the first (locking) direction, and serve to move the grips out of firm frictional engagement as ring 70 is rotated in the opposite direction. Stationary member 69 may be prevented from rotation by the aforementioned anti-rotation pin; and the latter may merely be a struck-out portion of a washer that is interposed between the stationary supporting means of the resistor and panel P and which washer is also prohibited from rotating by suitable means such as a rearwardly extending struck-out portion, all as indicated in an exemplary construction in the fragmentary sectional view portrayed in FIGURE 8. In that drawing the panel P is provided with a suitable hole or depression, Ph, evident at its front face and disposed to receive a rearwardly-extending tit or projection Wh struck out of a washer W that is interposed between panel P and member 60. The washer W carries also a forwardly-extending similar tit W or the like, disposed to fit in aperture 60b of member 60. Thus member 60 may be positively pre- 4;. cluded from rotating about the axis of the potentiometer. Obviously other equivalent means may be used to prevent member 60 from rotating and thus keep it stationary.

It will be noted that the outside apparent diameter at the forward end of grips 60g, even when those elements are in intimate frictional engagement with member 14, is somewhat greater than the minimum inside diameter of member 7%); and accordngly member may not inadvertently be removed from its intended position encircling member tl but is held from escape by the grips 60g. Also it will be noted that rotation of rotatable ring member 70 in a first (clockwise or right hand) direction as seen from in front of the potentiometer, causes application of the locking devices or grips 60g, whereas rotation in the opposite, second or left-hand direction causes release of the locking device, all as corresponds to tightening a nut on an ordinary bolt by rotating it in the right-hand direction and loosening it by rotation in the opposite direction. However, it will be evident that right-hand screw threads on member 60 and ring 70 could be used in a less preferable construction in which locking of the potentiometer would require rotation of ring 70 in a left-hand or counterclockwise direction. Further it is evident that the extent to which frictional engagement of grips 60g with member 14 is effected depends upon the extent to which ring member 70 is rotated, and hence that the frictional effect can be varied from that providing a slight drag, to that virtually providing a positive lock against rotation. Due to the low pitch of the screw thread and the nature of the construction, there is no tendency of ring 70 to rotate due to vibration, irrespective of whether the grips are engaged with the adjusting member, or not.

The preceding description of a specific exemplary illustrative embodiment of the invention evidences attainment of the noted objectives. In the light of the disclosure various modifications and changes within the true spirit and scope of the invention will occur to those skilled in the art, and hence we do not wish to have the invention restricted to the exact details of the exemplary embodiment except in accord with the scope of the appended claims.

We claim:

1. A variable resistor comprising:

first means, including stationary means arranged for attachment at a location thereon to a supporting panel or the like, and resistance element means supported on said stationary means;

second means, including a hollow rotatable part supported by said stationary means and adapted to be manually rotated about an axis for effecting adjustment of the variable resistor, said rotatable part having the characteristics of a knob and having a generally cylindrical exterior surface encircling said element means and said axis and extending generally forwardly from a region adjacent said location;

third means, including a stationary member having a generally cylindrical portion encircling said generally cylindrical exterior surface of said rotatable part and having an exteriorly threaded rear portion and a forward portion comprising a circular series of resilient flexible grips closely encircling said rotatable part and extending from said cylindrical portion with forwardly and outwardly rising cam surfaces and capable of flexing into and out of contact with said rotatable part, said third means comprising means to hold stationary said stationary member relative to said stationary means; and

fourth means, including a ring-like internally threaded member encircling and rotatable on said stationary member and adjacent said grips and having the thread thereof coacting with the thread of said stationary member and having rearwardly of said flexible grips a portion of diameter less than the maximum diameter of said series of grips and having a cam surface complementary to and engageable with said cam surfaces of said flexible grips whereby to force said grips inwardly into frictional engagement with said forward movement part incident to rotation of said ring-like member due to rotation thereof in a first direction;

whereby incident to rotation of said ring-like member in said first direction said grips are forced into frictional engagement with said rotatable part to hold the latter against rotation,

and whereby incident to rotation of said ring-like member in the opposite direction said grips are released from said hollow rotatable part.

2. A variable resistor according to claim 1, said stationary member being of cup-shaped configuration with a large mounting aperture in the bottom thereof and with an outstanding flange portion formed to provide said cylindrical portion and said flange portion being axially and radially slotted to provide said series of grips.

References Cited by the Examiner UNITED STATES PATENTS 2,047,219 7/1936 Meyer et a1 188--74 2,900,148 8/ 1959 Nickels. 3,025,931 3/1961 Jones 18883 3,069,646 12/1962 Hardison et a1 338-143 3,172,070 3/1965 Hardison et al. 338163 ANTHONY BARTIS, Primary Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,289,137 November 29, 1966 Robert L Jones et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 3, strike out "forward movement part incident to rotation of" and insert instead rotable part incident to forward movement of Signed and sealed this 19th day of September 1967.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner of Patents 

1. A VARIABLE RESISTOR COMPRISING: FIRST MEANS, INCLUDING STATIONARY MEANS ARRANGED FOR ATTACHMENT AT A LOCATION THEREON TO A SUPPORTING PANEL OR THE LIKE, AND RESISTANCE ELEMENT MEANS SUPPORTED ON SAID STATIONARY MEANS; SECOND MEANS, INCLUDING A HOLLOW ROTATABLE PART SUPPORTED BY SAID STATIONARY MEANS AND ADAPTED TO BE MANUALLY ROTATED ABOUT AN AXIS FOR EFFECTING ADJUSTMENT OF THE VARIABLE RESISTOR, SAID ROTATABLE PART HAVING THE CHARACTERISTICS OF A KNOB AND HAVING A GENERALLY CYLINDRICAL EXTERIOR SURFACE ENCIRCLING SAID ELEMENT MEANS AND SAID AXIS AND EXTENDING GENERALLY FORWARDLY FROM A REGION ADJACENT SAID LOCATION; THIRD MEANS, INCLUDING A STATIONARY MEMBER HAVING A GENERALLY CYLINDRICAL PORTION ENCIRCLING SAID GENERALLY CLYINDRICAL EXTERIOR SURFACE OF SAID ROTATABLE PART AND HAVING AN EXTERIORLY THREADED REAR PORTION AND A FORWARD PORTION COMPRISING A CIRCULAR SERIES OF RESILIENT FLEXIBE GRIPS CLOSELY ENCIRCLING SAID ROTATABLE PART AND EXTENDING FROM SAID CYLINDRICAL PORTION WITH FORWARDLY AND OUTWARDLY RISING CAM SURFACES AND CAPABLE OF FLEXING INTO AND OUT OF CONTACT WITH SAID ROTATABLE PART, SAID THIRD MEANS COMPRISING MEANS TO HOLD STATIONARY SAID STATIONARY MEMBER RELATIVE TO SAID STATIONARY MEMBER RELATIVE FOURTH MEANS, INCLUDING A RING-LIKE INTERNALLY THREADED MEMBER ENCIRCLING AND ROTATABLE ON SAID STATIONARY MEMBER AND ADJACENT SAID GRIPS AND HAVING THE THREAD THEREOF COACTING WITH THE THREAD OF SAID STATIONARY MEMBER AND HAVING REARWARDLY OF SAID FLEXIBLE GRIPS A PORTION OF DIAMETER LESS THAN THE MAXIMUM DIAMETER OF SAID SERIES OF GRIPS AND HAVING A CAM SURFACE COMPLEMENTARY TO AND ENGAGEABLE WITH SAID CAM SURFACES OF SAID FLEXIBLE GRIPS WHEREBY TO FORCE SAID GRIPS INWARDLY INTO FRICTIONAL ENGAGEMENT WITH SAID FORWARD MOVEMENT PART INCIDENT TO ROTATION OF SAID RING-LIKE MEMBER DUE TO ROTATION THEREOF IN A FIRST DIRECTION; WHEREBY INCIDENT TO ROTATION OF SAID RING-LIKE MEMBER IN SAID FIRST DIRECTION AND GRIPS ARE FORCED INTO FRICTIONAL ENGAGEMENT WITH SAID ROTATABLE PART TO HOLD THE LATTER AGAINST ROTATION, AND WHEREBY INCIDENT TO ROTATION OF SAID RING-LIKE MEMBER IN THE OPPOSITE DIRECTION SAID GRIPS ARE RELEASED FROM SAID HOLLOW ROTATABLE PART. 